I purchased a Trek Lime for my mother a few years ago. Unfortunately, it has now been stolen and I need to replace it. She has terrible arthritis so any bike that would require her hands to do more than hold on would be out of the question. I've considered buying a cruiser and having an automatic transmission such as the nexus hub installed, but I'm just not familiar enough with automatic transmissions to be sure this is even possible. To complicate matters, I'm working out of the country for the next year and a half so I have to rely on others. Does anyone have any suggestions? BTW--I'm not willing to spend thousands of dollars on it.

One option that I really recommend you, at least to consider, is a recumbent bike, specially one with a low crank and a relatively upright position.

With such a bike, not only the hands get much more relaxed, but also the butt benefit from a wide padded area for support, which is shared a bit with the lower back.

I have ridden a clone of the Easy Rider similar to this, and although I was very skeptical about the cumbersome looks of the bike, the comfort and ease are unbelieavable (to the point of asking myself why have I been torturing myself with regular bikes for so long).

For a senior lady I doubt there could be anything much better than this on two wheels (there are trike versions) BUT there are some caveats:

They are heavy;

They are cumbersome to manoeuver in tight spaces;

They require generous space for storage and to get in and out of house. A garage would be ideal;